Studies on the yeast nucleus : III. Properties of a deoxyribonucleoprotein complex derived from yeast

Abstract

1. A deoxyribonucleoprotein complex was isolated from Saccharomyces cerevisiae. It is composed of 36% DNA, 4% RNA and 60% protein. About 70% of the protein is acid-extractable. The complex sediments as a single band with a s°20,w of 27 S. 2. The yeast deoxyribonucleoprotein shows a biphasic melting profile. About 50% of the deoxyribonucleoprotein melts at 71° which is close to the Tm of DNA (68°) and 50% melts at 83°. When protein, mostly histone, was dissociated from the deoxyribonucleoprotein by extraction with NaCl of increasing concentrations, the percentage of deoxyribonucleoprotein melting at 83° decreases gradually, while the Tm of the remainder shifts to that of DNA. After dissociation of deoxyribonucleoprotein at 1 M NaCl, the melting profile is identical to that of yeast DNA. 3. The template activity for RNA synthesis of yeast deoxyribonucleoprotein was compared to that of yeast DNA using Escherichia coli RNA polymerase. The template activity is dependent on the concentration ratio of enzyme to template. A maximum template activity of 60% was observed for yeast deoxyribonucleoprotein at high concentration ratios of enzyme to template. 4. It is concluded that yeast deoxyribonucleoprotein resembles the deoxyribonucleoprotein of higher organisms in several aspects.